A cassette that accommodates an ink ribbon is well known in the art (see, for example, Japanese Patent Application Publication No. 2011-56755). A ribbon cassette described in the Publication '755 includes an ink ribbon wound about a ribbon spool. The ribbon spool is rotatably supported by an upper ribbon support part disposed in an upper case. A rotating member to which a clutch spring is mounted is disposed inside the ribbon spool. The rotating member restricts the ribbon spool from rotating in the direction opposite the direction for pulling ink ribbon off the ribbon spool by the elastic force (i.e., the rotational load) of the clutch spring.